Automatic transmissions used in modem automobiles typically utilize a sump filter to remove debris from transmission fluids. Sump filters generally comprise a filtering medium or media, and a filter housing. The filter housing can be formed of a variety of materials, including steel, aluminum, plastics and combinations thereof. Plastic filter housings in particular present numerous advantages. For example, compared to other filter housings, plastic filter housings weigh less, provide greater design flexibility and performance, and are recyclable. Accordingly, plastic filter housings are often more desirable than many other filter housings.
Various components can be connected to filter housings to improve filter performance. For example, adding one or more magnets to a filter housing greatly increases debris capture, as compared to using only laminated media to filter debris. Magnets remove large amounts of metallic particulates that might otherwise damage the transmission. Magnets are typically spaced apart from the filter housing and staked to posts located on the filter housing. Notably, spacing the magnets apart from the filter housing increases the surface area of the magnets that is available for capturing debris from the transmission fluid. This is because transmission fluid can flow across both the lower and upper surfaces of the magnet.
Magnets are typically connected to the posts by a heat-staking process. This involves sliding a magnet over two or more posts, and then heat-staking an individual retainer cap to each post. The retainer caps prevent the magnet from dislodging from the posts.
The above-described conventional methods of connecting a magnet to the filter housing present several drawbacks. One drawback is that an individual retainer cap must be welded to each post in order to secure the magnet. Separately heat-staking multiple caps increases the overall time required to assemble a filter housing, and therefore the overall cost of each filter housing. Another drawback is that the heat-staking process can create debris, such as flash, which can contaminate the transmission fluid. Yet another drawback is that the retainer caps can break off and allow the magnet to separate from the posts, thereby possibly occluding the inlet to the filter housing.